This invention relates generally to golf balls, and more specifically, to a golf ball having a cover comprising three or more layers.
The majority of golf balls commercially available today can be grouped into two general classes: solid and wound. Solid golf balls include one-piece, two-piece, and multi-layer golf balls. One-piece golf balls are inexpensive and easy to construct, but have limited playing characteristics and their use is usually confined to the driving range. Two-piece balls are generally constructed with a polybutadiene solid core and a cover and are typically the most popular with recreational golfers because they are very durable and provide good distance. These balls are also relatively inexpensive and easy to manufacture, but are regarded by top players as having limited playing characteristics. Multi-layer golf balls are comprised of a solid core and a cover, either of which may be formed of one or more layers. These balls are regarded as having an extended range of playing characteristics, but are more expensive and difficult to manufacture than are one- and two-piece golf balls.
Wound golf balls, which typically include a fluid-filled center surrounded by tensioned elastomeric material and a cover, are preferred by many players due to their spin and xe2x80x9cfeelxe2x80x9d characteristics but are more difficult and expensive to manufacture than are most solid golf balls. Manufacturers are constantly striving, therefore, to produce a solid ball that retains the beneficial characteristics of a solid ball while concurrently exhibiting the beneficial characteristics of a wound ball.
Golf ball playing characteristics, such as compression, velocity, xe2x80x9cfeel,xe2x80x9d and, therefore, spin, can be adjusted and optimized by manufacturers to suit players having a wide variety of playing abilities. For example, manufacturers can alter any or all of these properties by changing the materials (i.e., polymer compositions) and/or the physical construction of each or all of the various golf ball components (i.e., centers, cores, intermediate layers, and covers). Finding the right combination of core and layer materials and the ideal ball construction to produce a golf ball suited for a predetermined set of performance criteria is a challenging task.
Efforts to construct a multi-layer golf ball that has the benefits of both solid and wound balls have been numerous but manufacturers have generally focused on the use of cover layers formed of ionomeric compositions. It has been determined, however, that it is difficult to provide good xe2x80x9cfeelxe2x80x9d characteristics in a golf ball with the use of non-polyurethane materials, such as ionomers, which tend to provide a xe2x80x9cplastic feel.xe2x80x9d
It is desirable, therefore, to construct a golf ball formed of a thin urethane outer cover layer, at least two inner cover layers, and at least one core layer, according to the present invention. In particular, it is desired that this construction produce a multi-layer golf ball having variable spin rates, based on predetermined ball construction, while providing the golfer with good xe2x80x9cfeelxe2x80x9d characteristics generally associated with other conventional ball constructions.
The present invention is directed to a golf ball comprising a core and a cover, wherein the cover includes an inner cover layer being disposed directly adjacent the core; an outer cover layer having a thickness less than about 0.050 inches; and an intermediate cover layer is disposed between the inner and outer cover layers; wherein at least one of the inner, intermediate, or outer cover layers is a dense layer having an inner diameter of at least 38.4 mm, a specific gravity greater than about 1.2 and a thickness between about 0.025 mm and about 1.27 mm.
The outer cover layer includes a composition formed of a reactive liquid material. The dense layer has a specific gravity of at least about 1.5, more preferably at least about 1.8, and most preferably at least about 2.0. The dense layer can include polyurethanes, polyureas, polyurethane ionomers, epoxies, polyesters, silicones, rubber latex, or a mixture thereof, or, alternatively, a thermoplastic polymer. The dense layer has a hardness of at least about 30 Shore D, more preferably at least about 50 Shore D, and most preferably at least about 60 Shore D.
The thermoplastic material for the dense layer includes polyolefins, polyethylene, polypropylene, polybutylene, polyethylene acrylic acid copolymers, polyethylene methacrylic acid copolymers, polyethylene methacrylic acid terpolymers, polyethylene acrylic acid terpolymers, polyethylene ethyl acrylate, polyethylene methyl acrylate, polyethylene vinyl acetate, polyethylene glycidyl alkyl acrylate, ionomers fully or partially neutralized by a metal ion or a salt of an organic acid, metallocenes, polyesters, polyamides, thermoplastic elastomers, copolyether-esters, copolyether-amides, thermoplastic polyurethanes, or a mixture thereof.
The thin dense layer is positioned at a distance ranging from 0.76 mm to 2.8 mm from the land surface of the ball and has a thickness of from 0.127 mm to 0.76 mm, preferably between about 0.25 mm and about 0.5 mm. The dense layer can include a densified loaded film or a thermoplastic polymer loaded with a specific gravity increasing agent, preferably tungsten powder. Alternatively, the dense layer is applied to the core as a liquid solution. preferably, the dense layer is formed by compression or injection molding, reaction injection molding, casting, spraying, dipping or powder coating.
The core is a non-wound core having a specific gravity of less than the specific gravity of the dense layer, a diameter between about 35 mm and about 42 mm, and a compression of less than about 90. In one embodiment, the inner cover is the dense layer and the intermediate and outer cover layers each have a specific gravity less than the dense layer. In an alternative embodiment, the intermediate layer is the dense layer and the inner and outer cover layers each have a specific gravity less than the dense layer.
The dense layer may also be a non-continuous layer and the core has a specific gravity of less than about 1.1. The non-continuous layer has a specific gravity greater than about 1.8, preferably greater than about 2.0. The golf ball may further include a second dense layer directly abutting the non-continuous layer.